The invention relates to a vaporization burner for a heating device such as a heating device for vehicles operated with liquid fuel, especially oil, having combustion chamber within which a carrier connected with a fuel line and receiving an absorbent body is disposed.
Evaporation burners of the initially mentioned type have been known from U.S. Pat. No. 3,531,229 and German Auslegeschrift No. 21 29 663. In these burners, the carrier for the absorbent body is formed directly by one of the front walls of the combustion chamber which, itself, is in heat conducting connection with the outer housing of the burner.
In my co-pending U.S. application Ser. No. 516,381, filed July 22, 1983 now U.S. Pat. No. 4,530,658, a vaporization burner has been described which ensures a quick conversion of the liquid fuel into the vapor form, even in the case of combustion chambers having particularly small dimensions. For this purpose and in the case of this vaporization burner, the carrier in the combustion chamber is supported in a manner that is protected against dissipation of heat therefrom. Preferably, an air cushion is provided between the carrier and the adjacent combustion chamber wall.
In German Auslegeschrift No. 18 03 815, a carbonization insert for burner arrangements for burning liquid fuel is disclosed which is disposed in the combustion chamber. With this arrangement, by an even temperature distribution, carbonization is prevented and a blue burning of the liquid fuel achieved. In this case, the insert is developed as a heating pipe or "heat pipe", that has a metallic jacket which encloses a hollow space tightly on all sides and in which a small quantity of evaporable liquid is located. The liquid which may, for example, be liquid sodium, evaporates during heating and distributes the heat on the entire surface of the heating pipe so that the combustion chamber space, in its entire extent, may be kept at an evenly high temperature. Thus, the temperature at which the undesirable carbonization takes place no longer occurs. Such "heat pipes" have a heat conductive capacity up to 10,000 times the heat conductive capacity of copper. Such a known heat pipe serves, therefore, for a quick carrying off and distribution of heat with the goal of avoiding local hot spots.
In the case of vaporization burners of the initially stated type, it has turned out that the carrier, especially when the heating device operates for a short duration and especially in the case where oil is used as the fuel, the vaporization temperature required for vaporization of the fuel will not always be achieved since, for example, combustion residues deposited on the carrier lead to a thermal isolation of said residues. Also in the case of heating oil and diesel oil, the vaporization temperature range lies in the range of 180.degree. to 350.degree. C., while in the case of gasoline, a vaporization temperate range of 35.degree. to 200.degree. C. suffices.
In order to bring about a solution for the difficulties mentioned previously, the invention has a principal object of creating an evaporation burner of the initially cited type wherein the temperature required for vaporization of the fuel will be reached reliably and quickly independently of any deposit of combustion residues on the carrier, especially in the case of operating the evaporation burner with oil. This object is achieved, in accordance with preferred embodiments of the invention, by providing a heat conducting body of heat resistant, heat conductive material on the carrier in a manner projecting into the flame zone of the combustion chamber.
This heat conducting body on the carrier according to the invention makes it possible for the vaporization burner to operate reliably even in the case of short duration operation of the heating device. Because of its good heat conducting capacity, the heat conducting body conducts the heat from the flame zone of the combustion chamber to the carrier surface and, therefore, makes possible a quick heating up of this surface to the required vaporization temperature which, in the case of operating the vaporization burner with oil, such as heating oil or diesel oil, lies in the range of 180.degree. to 350.degree. C., even if combustion residues have been deposited on the carrier. Furthermore, since the free end of the heat conducting body projects into the flame zone of the combustion chamber, an additional temperature increase occurs at this end as a result of the improvement of the combustion reaction of the fuel/air mixture. Thus, the temperature difference between the surface of the carrier on which the heat conducting body is disposed and the free end of the heat conducting body is relatively great, so that on the basis of this temperature gradient, a very quick heating up of the surface of the carrier with the help of the heat conducting body will be achieved.
In accordance with the invention, various manners of attachment of the heat conducting body to the carrier surface are possible. One very simple attaching method, as far as manufacturing engineering is concerned, is to attach the heat conducting body to the carrier by means of pressure welding. This pressure welding may be carried out in a single operation.
Likewise, in accordance with the preferred embodiments, variations in the construction of the heat conducting body itself, are possible whereby, dependent on the existing conditions of space and in view of the weight of the vaporization burner. For example, the heat conducting body may be developed as a hollow body. In such a case, it is advantageous for the heat conducting body to be closed at one end in order to achieve a distribution of the heat in the area of the flame zone of the combustion chamber over the entire cross sectional surface of the hollow body. A particularly effective manner of closing the free end of the hollow heat conducting body is in such a way that a pointed end will be formed, whereby the walls of the pipe in the area of this pointed end are directly in contact with one another, in order to achieve a heat conduction from this point distributed over the entire wall surface of the hollow body to the carrier surface.
In order to improve the vaporization of the fuel, according to a further feature, the area of the carrier around the heat conducting body is not covered by the absorbent body, so that a fuel film is formed on the exposed surface of the carrier and is vaporized directly from the carrier with the help of the heat conducting body.
In dependence on the constructional conditions of the vaporization burner, it is also contemplated that the heat conducting body may be disposed centrally or eccentrically on the carrier surface. As a result, it is possible for the heat conducting body to be disposed on the carrier in such a way that other features of existing burners such as a glow arrangement and/or additional arrangements, such as a flame monitor or the like, will not have to be restructured or modified to accommodate a carrier with the heat conducting body according to this invention.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.